The Climate System

Copyright 2000 Academic Press Limited All rights of reproduction in any form reserved 

Heat transfer processes besides pure radiative transfer are involved in control of the temperature of the air, especially below the effective emission height of 6 km. Referring back to Chapter 7, we see that vertical motions of air in the troposphere are a main factor dictating that temperature decreases as altitude increases - air loses internal energy 

These two points taken together illustrate that the temperature at the Earth s surface depends on bofh a radiative balance and all of the meteor-ologic processes that transport heat within the lower atmosphere and of course, all the oceanographic factors that transport heat in the ocean as well. So, at this juncture we must abandon the simple picture of a global-mean radiative heat 

Keeping in mind the entire set of components in the climate system as depicted in Figs 17-2,4-13, and 17-3, we can now re-examine Fig. 1-2 to emphasize that biogeochemical cycles are coupled with the climate system. The temperature (as inferred from the record of the deuterium to hydrogen ratio in Antarctic ice) covaries with CO2, CH4 and other species that derive from biological processes. Two simple, if extreme, possibilities can be drawn  

Changes in physical climate cause changes in biological activity, but not vice versa or 

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The ocean is an integral part of the climate system. It contains almost 96% of the water in the Earth s biosphere and is the dominant source of water vapour for the atmosphere. It covers 71% of the planet s surface and has a heat capacity more than four times that of the atmosphere. With more than 97% of solar radiation being absorbed that falls on the surface from incident angles less than 50" from the vertical, it is the main store of energy within the climate system. 

DMS has been observed in the marine atmosphere since the early 1970s, but it was not until the mid-1980s that there was interest in this gas as being a natural source for sulfate CCN. Sulfate aerosols are, in number terms, the dominant source of CCN. The major role clouds play in the climate system leads to possible climatic implications if changes to DMS production occurred. Furthermore, the dependence of this production on environment conditions means that scope for a feedback process arises this feedback is called the Charlson hypothesis. ... 

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. 

In its assessment of climate change, the IPCC (1990) identified five hydrosphere-related feedback mechanisms in the climate system likely to be activated by increased greenhouse gas concentrations in the atmosphere. These feedbacks are briefly described below for more detailed discussion of the climate system, refer to Chapter 17. 

Clouds. Cloud feedback mechanisms are among the most complex in the climate system, due to the many disparate roles played by clouds, which control a large portion of the planetary albedo but also trap terrestrial radiation, reducing the energy escaping to space. To complicate matters further, different t5 es of clouds behave differently in the same environment. In the present climate mode, clouds have... 

The El-Niho southern oscillation (ENSO) phenomenon is an interannual perturbation of the climate system characterized by a periodic weakening of the trade winds and... 

The Dynamics of the Climate System Forcings, Feedbacks, and Responses... 

Changes in the physical characteristics of the Earth that are internal to the climate system can... 

The nature of such processes can be depicted as a feedback loop, as shown in Fig. 17-4. Using the nomenclature in this figure and continuing with enhanced evaporation of water vapor as our physical example of a feedback that is completely internal to the climate system, we... 

While most climate models consider feedbacks as being dependent on temperature (usually Ts), there are many other dependent variables in the climate system that could be involved, for example solar irradiance at the ground or rainfall. However, it is customary to describe these mathematically as functions of Tg,... 

Fig. 17-4 Schematic of the climate system with and without feedbacks, that depend on temperature.

Recent revisions to the boundary conditions (ice-sheet topography and sea surface temperatures) have added uncertainty to many of the GCM calculations of the past two decades. Moreover, all of these calculations use prescriptions for at least one central component of the climate system, generally oceanic heat transport and/or sea surface temperatures. This limits the predictive benefit of the models. Nonetheless, these models are the only appropriate way to integrate physical models of diverse aspects of the Earth systems into a unified climate prediction tool. 

The Fifth Assessment Report from the Intergovernmental Panel on Climate Change states that human influence on the climate system is clear [1], The C02 concentration in the atmosphere is continuously growing. The latest value is 402.52 ppm (January 2016, Mauna Loa Observatory), which is 2 pmm higher than the value registered in January 2015 [1],... 

I apply these computational methods to various aspects of the Earth system, including the responses of ocean and atmosphere to the combustion of fossil fuels, the influence of biological activity on the variation of seawater composition between ocean basins, the oxidation-reduction balance of the deep sea, perturbations of the climate system and their effect on surface temperatures, carbon isotopes and the influence of fossil fuel combustion, the effect of evaporation on the composition of seawater, and diagenesis in carbonate sediments. These applications have not been fully developed as research studies rather, they are presented as potentially interesting applications of the computational methods. 

Significant economies of computation are possible in systems that consist of a one-dimensional chain of identical reservoirs. Chapter 7 describes such a system in which there is just one dependent variable. An illustrative example is the climate system and the calculation of zonally averaged temperature as a function of latitude in an energy balance climate model. In such a model, the surface temperature depends on the balance among solar radiation absorbed, planetary radiation emitted to space, and the transport of energy between latitudes. I present routines that calculate the absorption and reflection of incident solar radiation and the emission of long-wave planetary radiation. I show how much of the computational work can be avoided in a system like this because each reservoir is coupled only to its adjacent reservoirs. I use the simulation to explore the sensitivity of seasonally varying temperatures to such aspects of the climate system as snow and ice cover, cloud cover, amount of carbon dioxide in the atmosphere, and land distribution. 

I use the seasonal simulation to explore the sensitivity of this energy balance climate model to such features of the climate system as permanent ice and snow at high latitudes, seasonal ice and snow, cloud cover, carbon dioxide amount, and the distribution of the continents. 

The climate is an important aspect of the environment, an aspect that interacts strongly with the composition of the ocean and atmosphere. This interaction works in two ways Climate is influenced by composition through the greenhouse effect, and climate also influences composition through its effect on reaction rates, particularly on weathering and the flux of dissolved constituents into the sea. Full-scale climate models are exceedingly complicated and can run only on supercomputers. But here I shall demonstrate how one aspect of the climate system—average tern-... 

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